Name ________________________________________ Date ___________ Period ______ Page ___
Average Atomic Mass
1. A sample of Element X is found to contain 77.38% of the isotope type1 (83.1243 amu)
and 22.62% of isotope type 2 (87.4927 amu). Calculate the average atomic mass of Element
2. Three isotopes of argon occur in nature: argon- 36, argon-38, and argon-40. Calculate the
average atomic mass of argon to two decimal places, given the following relative atomic masses
and abundances of each of the isotopes: argon-36 (35.97 amu; 0.337%), argon-38 (37.96 amu;
0.063%), and argon-40 (39.96 amu; 99.600%).